This invention relates to an improved apparatus for dispensing pasty substances, such as in particular silicone, which are contained in tube-like flexible sealed vessels.
It is commonly appreciated that dispensing pasty substances both in industrial applications and at home is a duty having a number of prerequisites, i.e. easy and convenient use by a single operator, capability of dispensing the paste as a continuous, uninterrupted extruded strip that will break off abruptly and neatly as soon as the operator stops dispensing at his/her will, permanent separation of the paste to be dispensed from the air even for prolonged periods of time (so as to avoid interactions of the air with the substance to be dispensed, such as for instance silicone), and convenience in handling and reloading the dispensing apparatus.
Although many types of manually operated dispensers can meet these requirements, it becomes somewhat difficult to provide for such requirements in the case of dispensers that have to be used or operated with a single hand and that need to be particularly simple and low-cost in order to be feasible for use on an industrial scale.
Currently, the most widely used dispensing devices are manually operated dispensing guns in which a sealed cartridge containing the substance to be dispensed is inserted. The sealed cartridge terminates at its front dispensing end with a sealed spout, which is cut open immediately before using the gun, and at its opposite end with a substantially hermetically sealed element acting as a moving cap. The cap is disposed in the rear side of the outer casing of the cartridge so as to be capable of sliding forward under the thrusting action of a dispensing plunger.
The cartridge is loaded by inserting the same into the gun-type dispensing apparatus so that, upon closing the apparatus, the plunger is brought against the sealing element of the cartridge.
To operate such a type of dispensing apparatus, all that is then needed is to unseal the front dispensing spout, and operate a lever of the gun so that it acts on the plunger element. The plunger element, moving forward due to the actuation of the lever, pushes the sealing element forward toward the front dispensing spout so that the paste contained in the cartridge is ultimately squeezed out of the spout.
When there is no more paste left in the cartridge due to repeated dispensing, the plunger element is extracted from the body of the dispensing apparatus, while the empty cartridge is then replaced with a new, full cartridge, so that the above-described dispensing procedure may be restarted.
Because such dispensing apparatus are widely known, there is no need to describe them here any further.
These dispensing apparatus perform in a satisfactory way in cases of limited use or when there are no particular handling or maneuverability problems to be encountered. Conversely, when it comes to industrial applications, the following drawbacks appear to be associated therewith.
1) High costs. As a matter of fact, the cartridge containing the paste to be dispensed is usually made as a rigid plastic molding and, notwithstanding its altogether high costs, it is inevitably thrown away when emptied. In applications requiring great amounts of paste to be dispensed and, as a consequence, the use of a large number of cartridges, the ultimate expense that must be sustained for such one-way cartridges is certainly quite considerable.
2) Poor convenience in handling. When working in large structures, such as buildings, the operator needs to use tools that are very convenient to handle, compact and operable with a single hand, since it quite often occurs that the other hand needs to be used to keep the workpiece in place or the operator in a stable position. Dispensing guns of the traditional type are rather cumbersome and quite often require the use of both hands at the same time.
3) Poor cleanliness. When used intensively, traditional dispensing guns tend to allow the paste to seep through the inside the vessel of the apparatus containing the cartridge, thereby clogging it up or, anyway, making it more difficult and time-consuming to replace the cartridge.